This invention relates to a thermal recording medium, and more particularly, to a thermal recording medium good in recording sensitivity and recording stability.
The present invention can be effectively applied to recording wherein figures and the like are printed to correspond to magnetically recorded contents in a prepaid magnetic card such as a telephone card so that the magnetically recorded contents may be visually recognized.
Conventionally, there are two methods for recording information on a recording paper by heating the heating element of a thermal head at desired timing according to recording signals while scanning said thermal head over the recording paper. These methods are: a heat transcription method in which a desired pattern is transcribed on a normal recording paper by heating and melting the ink of a heat sensitive ink ribbon which is interposed between a thermal head and the recording paper; and a thermal method in which a thermal recording paper is colored in a desired pattern.
The thermal method is advantageous in that since ink is not applied to a recording paper, and the heat sensitive layer of the recording paper itself is colored, the printed record is hardly affected adversely even when external frictional force is applied to the recording paper after recording, and in addition no ink ribbons are necessary.
However, in the conventional thermal method, since recording is effected based on chemical changes in a heat sensitive color forming layer, and the chemical changes are reversible, the record may change under some circumstantial conditions after the recording, and therefore the thermal method is accompanied by a problem that the record is not stable.
In order to solve such a problem, a new heat sensitive recording method is suggested wherein, instead of a recording paper having a heat sensitive color forming layer as mentioned above, a recording medium having a metal thin layer, a heat sensitive softening layer positioned in contact with the metal thin layer, and a contrasting layer is used, while the recording medium is scanned by a thermal head and heating elements are heated at suitable timing so that desired positions of the metal thin layer may be heated and melted to allow the metal thin layer to be dispersed at said desired positions as fine particles into the heat sensitive softening layer which has been softened thereby causing the metal thin layer and the contrasting layer to be contrasted visually at said desired positions and the remaining positions for recording.
However, in this method since it is required to melt the metal thin layer, a large amount of heat is needed for sufficiently favorable recording, that is, this method is defective in that the recording sensitivity is not sufficient.